This invention relates generally to television receivers and more particularly to an "instant play" device for enabling a television receiver to achieve a normal brightness video display shortly after being energized.
Television receivers, in general, include a cathode ray tube which reaches its full brightness capability only after an initial warm-up period during which its cathode reaches operating temperature. Such a warm-up period may extend for two to three minutes following the initial energization of the receiver.
Most receivers manufactured today employ all solid-state electronics which essentially have no warm-up time. Thus the picture tube is the only vacuum tube having a heater. This exacerbates the problem since the remainder of the receiver is functioning normally as soom as it is turned on and the video display slowly comes up to brightness.
In order to provide consumers with a more nearly "instant" picture, a number of so-called "instant play" devices or circuits have been proposed. According to one such proposal, the warm-up period for the cathode ray tube has been substantially reduced or even eliminated by providing stand-by power to maintain the cathode of the cathode ray tube at or near its normal operating temperature when the television receiver is off. When the receiver is turned on, no warm-up period is required and an "instant" picture is provided. However, the use of stand-by power is wasteful of energy, expensive and illegal in some states.
Other "instant play" proposals for reducing the time interval between the initial energization of a cathode ray tube and the time at which the cathode ray tube produces a normal brightness display have included relatively expensive circuit components or have required the existing circuitry in a television receiver to be substantially modified. In the latter case, the "instant play" device cannot be conveniently used as an add-on feature without at least some redesign of the receiver.
The shortcomings noted above in present or proposed "instant play" circuits render those circuits undesirable from the standpoint of operating efficiency or manufacturing expense.